1. Field of the Invention
The present invention relates generally to a mobile communication device capable of improving low sound performance and more particularly to a mobile communication device having a speaker module.
2. Description of Related Art
A mobile communication device including a mobile phone or a PDA is one of many mobile electronic devices allowing a user to wirelessly transmit, receive, read, or process information while traveling.
Spurred by the recent advancement of the information technologies, communication technologies, and memory technologies, mobile communication devices can directly create, transmit, or receive multimedia, in addition to their inherent call functions. For example, mobile communication devices can reproduce multimedia files such as music, movies or games, and even have a function of receiving digital multimedia broadcasting (DMB) using satellite or terrestrial television channels. For those mobile communication devices equipped with a digital camera, the devices can also capture images or videos, transmit images or video, or otherwise allow users to enjoy the images or video obtained using the digital cameras.
To help users enjoy the multimedia experience through the mobile communication devices, speakers mounted in the mobile communication devices are moving towards providing high sound performance. Meanwhile, the mobile communication devices are becoming lighter and thinner for user's convenience in carrying them around, which may cause problems as more sophisticated speakers are incorporated into the mobile communication devices. Therefore, there is a need to provide a speaker unit that does not take up unnecessarily excessive space in the mobile communication device but still provides higher sound performance.
The speaker unit of the related art mobile communication device will now be described with reference to FIG. 1. FIG. 1 is a sectional view showing a speaker portion of the related art mobile communication device. As shown in FIG. 1, the mobile communication device 11 includes first and second housings 12 and 13 supporting internal components and forming the exterior thereof, and a speaker unit 16 is fixed at an inner side of the second housing 13.
Through holes 15 are formed on the second housing 13 to allow a sound (A) emitted from a front surface of the speaker unit 16 to pass therethrough, and accordingly, sound waves are discharged to the exterior after passing through the through holes 15.
Ribs 14 are formed on an inner surface of the second housing 13 to fix the speaker unit 16, and the speaker unit 16 is tightly attached to the ribs 14 so that the sound emitted from its front side cannot be leaked to the interior of the mobile communication device.
Gaskets 17 are installed at an inner side of the ribs 14 to ensure the speaker unit 16 to be tightly attached. With such a structure, the speaker unit 16 generates sounds A and B according to signals transmitted from a board 18 provided within the housings 12 and 13. However, one of the problems with the above configuration is that the sound (A) emitting from the front side of the speaker unit 16 is interfered with by the sound (B) generated from the rear surface of the speaker unit 16 and having the opposite phase, thereby degrading the performance of the speaker unit 16. In other words, in case of a low band, because it has strong diffraction, the sound (A) generated from the front side and the sound (B) generated from the rear side having the opposite phase to that of the sound (A) are mixed and cancel each other out.